Identifying Transmission Lines on a 2003 Chevy Silverado with 5.3 Liter and Cooler Recommendations

Question:

I am interested in adding the Derale cooler #13504 to my 2003 Chevy Silverado w/5.3 L engine and auto trans with the OEM tow package. It has an OEM tranny cooler mounted about 2 inches front of the condenser and the radiator. Theres lots of extra space around it. The OEM cooler has 2 lines that enter from the bottom. I assume one of these is the feed and the other the return. Which line is the return? Passenger or drivers side? Can the splice be made here leaving the OEM cooler in the series? If not where will I need to make the splice? Will turbulence created by the this cooler have a negative affect on the cooler, condenser and radiator behind it? ie Make them work harder to do their job or reduce their efficiency? Which adapter fittings will I need? Id prefer vehicle specific fittings if offered, rather than generic hose fittings.

asked by: Anthony S

Expert Reply:

I had a vehicle with this same engine and had a transmission cooler to it. The easiest way to find the correct lines going to and from the transmission is to start the motor and put it in drive for about 10 seconds or so. Then, put the vehicle back in park and turn off the motor. Under the truck feel both lines from the transmission. One will be warmer the other cooler to the touch. The cooler one is the return line.

A supplemental cooler installs in line after the factory cooler. So the flow will go from the transmission, to the factory cooler, then to the supplemental cooler, and back to the transmission. A transmission cooler like # D13504, is a flow through device meaning air flow will be able to pass through it and on to the components behind it with little to no efficiency lost.

For a fitting, you could use # D13018. This will allow you to connect the radiator to the cooler quickly and easily.

Another option is to use a pan cooler, # D14207. This mounts below the vehicle to the transmission in place of the factory pan. It will fit if your truck has the 4L80E transmission. Tubes in the bottom of the pan allow air to flow through them cooler fluid by as much as 20 to 50 degrees Fahrenheit. I have included some links to FAQs on transmission cooler for you.

expert reply by: Michael H